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Model
R-84ST (serv.man6)
Pages
30
Size
1.12 MB
Type
PDF
Document
Service Manual
Brand
Device
Home Appliance / Microwave Oven / Complete
File
r-84st-sm6.pdf
Date

Sharp R-84ST (serv.man6) Service Manual ▷ View online

R-84STM - 5
ITEM
DESCRIPTION
Power Requirements
230 - 240 Volts / 50 Hertz / Single phase, 3 wire earthed
Power Consumption
Microwave cooking                          1.45kW Approx. 6.5A
Dual cooking
(Microwave and Top Grill)                2.4kW Approx. 10.4A
(Microwave and Bottom grill)            1.95kW Approx. 8.5A
(Microwave and Convection)            2.4kW Approx. 10.4A
(Top and Bottom Grill)                      1.55kW Approx. 6.3A
Convection cooking                          2.08kW Approx. 9.1A
Grill Cooking
(Top Grill)                                        1.05kW Approx. 4.2A
(Bottom Grill)                                        0.55kW Approx. 2.3A
Power Output
900 watts nominal of RF microwave energy (measured by method of IEC
60705) Operating fequency 2450 MHz
Grill heating element Power Output
Top Grill 1.kW
Bottom Grill 0.5kW
Case Dimensions
Width 520 mm
Height 309 mm (including foot)
Depth 488 mm
Cooking Cavity Dimensions
Width 349 mm
Height 207 mm
Depth 357 mm
Turntable diameter
325mm
Control Complement
Touch Control System
Microwave Cooking Control
Repetition Rate;
HIGH .............  Full power throughout the cooking time
MEDIUM HIGH .............  approx. 70% of FULL Power
MEDIUM .......................  approx. 50% of FULL Power
MEDIUM LOW ..............  approx. 30% of FULL Power
LOW .............................  approx. 10% of FULL Power
TIME keys                                     STOP/CLEAR key
INSTANT COOK keys                   KITCHEN TIMER/CLOCK SET key
EXPRESS COOK keys                  WEIGHT CONVERSION key
EXPRESS DEFROST keys           WEIGHT keys
MEAL IN
 O
NE keys                      MICRO. POWER key
CONV. (
0
C) key                             GRILL key
DUAL CONV./GRILL key
LESS(
)/MORE(
) keys
INFO keys
START/AUTO MINUTE key
Net Weight
Approx. 20 kg
SPECIFICATION
As part of our policy of continuous improvement, we reserve the right to
alter design and specifications without notice
Note:
Temperature measurements taken whilst the oven is in convection mode will differ from the displayed level.
This is due to the grill elements turning on and off in order to regulate the oven temperature.
This will not affect the cooking results as long as the operation manual and cook book are followed correctly.
R-84STM - 6
OFF CONDITION
Closing the oven door activates all door interlock switches
(monitored latch switch and stop switch).
IMPORTANT:
When the oven door is closed, the contacts COM-NC of the
monitor switch SW2 must be open and the contacts (COM-
NO) must be closed. When the microwave oven is plugged
into a wall outlet (230-240V / 50Hz), 230-240 volts A.C. is
supplied to the point A1 + A3 in the control unit.
1. The display starts demo mode.
2. To set any programmes or set the clock, you must first
touch the STOP key.
3. Information appears on display.
NOTE: When the oven door is opened, the oven lamp
comes on at this time.
MICROWAVE COOKING CONDITION
HIGH COOKING
Enter a desired cooking time with the Time keys and start the
oven with touching START key.
Function sequence Figure O-1 on page 18
CONNECTED COMPONENTS
RELAY
Oven lamp, Turntable motor
RY1
High voltage transformer
RY2
Fan motor
RY6
1 When the cooking time is up, a signal tone is heard and
the relays RY1 + RY2 + RY6 go back to their home
position. The circuits to the oven lamp, high voltage
transformer, fan motor and turntable motor are cut off.
2. When the oven door is opened during a cooking cycle,
the switches come to the following condition.
Switch
Contact
          Condition
During
Oven Door
Cooking
Open(No cooking)
 Monitored latch Switch COM-NO
Closed
Opened
 Monitor Switch
COM-NO
Closed
Opened
 Monitor Switch
COM-NC
Opened
Closed
Stop switch
COM-NO
Closed
Opened
The circuit to the high voltage transformer, is cut off when the
contact of relay RY2 contacts COM-NO of the monitored
latch switch SW1, and monitor switch SW2 are made open.
The circuit to the fan motor is cut off when the relay RY6 is
made open. The circuit to the turntable motor is cut off when
the contacts COM-NO of the monitor switch are made open.
The relay RY2 and RY6 are made open when the door is
opened. The oven lamp remains on even if the oven door is
opened after the cooking cycle has been interrupted, because
the relay RY1  stays closed. Shown in the display is remaining
time.
3. MONITOR SWITCH CIRCUIT
The monitor switch SW2 is mechanically controlled by
the oven door, and monitors the operation of the monitored
latch switch SW1.
3-1. When the oven door is opened during or after the cycle
of a cooking program, the monitored latch switch SW1
and stop switch SW3 must open their contacts (COM-
NO) first. After that the contacts (COM-NC) of the
monitor switch SW2 can be closed and the contacts
(COM-NO) of monitor switch SW2 are made open.
3-2. When the oven door is closed. The contacts (COM-NC)
of the monitor switch SW2 must be opened and the
contacts (COM-NO) of monitor switch SW2 must be
closed. After that the contacts of the monitored latch
switch SW1 and the stop switch SW3 are made closed.
3-3. When the oven door is opened and the contacts of the
monitored latch switch SW1 remain closed, the fuse F2
F8A will blow. Because the relay RY1 and monitor
switch SW2 are closed  and a short circuit is caused.
3 seconds  are needed for heating up the
magnetron filament.
32 sec. ON
24 sec. ON
18 sec. ON
12 sec. ON
6 sec. ON
8 sec. OFF
14 sec. OFF
20 sec. OFF
28 sec. OFF
HIGH
MEDIUM
 HIGH
MEDIUM
MEDIUM 
LOW
LOW
Approx. 70%
Approx. 50%
Approx. 30%
Approx. 10%
Approx. 100%
MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW
COOKING
When the microwave oven is preset for variable cooking
power, the 230-240 volts A.C. power is supplied to the high
voltage transformer intermittently within a 32-second time
base through the relay contact which is coupled with the
current-limiting relay RY2. The following levels of microwave
power are given.
Note: The On/Off time ratio does not exactly correspond to
the percentage of microwave power, because approx.
Approx 100%
OPERATION SEQUENCE
R-84STM - 7
TEST PROCEDURES
SENSING FIRE OPERATION
The oven will stop its operation when there is a fire in the
oven cavity in microwave cooking condition.
LSI measures the voltage across the temperature measure-
ment circuit intermittently within a 32-second time base once
the oven is started in the microwave cooking mode. The oven
will stop its operation when the difference of the voltages is
more than 0.69 volts in microwave cooking condition.
1. Within a 32-second base, first the thermistor is energized
for 3 seconds.  After 2 seconds since the thermistor is
energized, the voltage across the temperature
measurement circuit is measured. And after 21 seconds
since the thermistor is cut off, the convection motor
operates for 10 seconds.
2. The oven carries out the procedure above again. If the
second voltage is 0.69V higher than the first voltage, LSI
judges it is a fire in the oven cavity and stops the oven.
3. When sensor cooking, the sensing fire operation is not
carried out until the oven senses the steam from food.
Because food cannot be cooked well by rotating the
convection fan at that time. After sensing the steam, the
sensing fire operation is started.
CONVECTION
MOTOR
THERMISTOR
Sensing 
Voltage
ON
OFF
ON
OFF
ON
OFF
0 2
20
30 32
64 (sec.)
3 sec.
Sensing the voltage across temperature measurement circuit.
4. When LSI judges it is fire in the oven cavity, LSI will switch
off the relays to the power transformer, fan motor and
convection motor and LSI stops counting down. And then
the damper is closed so that the fresh air does not come
into the oven cavity.
MICROWAVE OUTPUT POWER (IEC-60705)
The power output of this oven is rated using the method specified by IEC-60705.  Full details of how to carry out this
procedure can be found in the Sharp Technical Training notes which is available from Sharp Parts Centre
(part number SERV-LITMW01).
The IEC-60705 procedure must be carried out using laboratory-type procedures and equipment.  These requirements
make the procedure unsuitable for routine performance checks.
Note: The following test method gives an indication of the output power only, it cannot be used to establish the actual/
rated output power.  If the true output power is required, then the IEC-60705 test method must be used.
Alternative simplified method:
1. Place 2 litres of cold water (between 12
°C and 20°C) in a suitable container.
2. Stir the water and measure the temperature in 
°C.  Note temperature as T1.
3. Place the container in the microwave and heat the water for 2 minutes on full power.
4. When the 2 minutes is completed, remove the container and stir the water.  Note the water temperature as T2.
5. Calculate the output power using the following formula:
R.F. Power Output = (T2 - T1) x 90.
MICROWAVE LEAKAGE TEST
This oven should be tested for microwave leakage on completion of any repair or adjustment, following the procedure
described in the Sharp Technical Training notes (part number SERV-LITMW01).  The maximum leakage permitted in
BS EN 60335-2-25 is 50W/m
(equivalent to 5mW/cm
2
), however it is not normal to detect any significant leakage,
therefore, any leakage which is detected should be investigated.
It is essential that only leakage detectors with current calibration traceable to the National Physical Laboratories are
used.
Suitable leakage detectors :
CELTEC A100
APOLLO X1
TEST PROCEDURES
R-84STM - 8
PROCEDURE
LETTER
COMPONENT TEST
A
TOUCH CONTROL PANEL ASSEMBLY TEST
TEST PROCEDURES
B
KEY UNIT TEST
The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore,
unlike conventional microwave ovens, proper maintenance can not be performed with only a voltmeter and
ohmmeter.
In this service manual, the touch control panel assembly is divided into two units, Control Unit and Key Unit,
and also the Control unit is divided into two units, CPU unit and Power unit, and troubleshooting by
replacement is described according to the symptoms indicated.
1.  Key Unit   Note : Check key unit ribbon connection before replacement.
The following symptoms indicate a defective key unit. Replace the key unit.
a) When touching the pads, a certain pad produces no signal at all.
b) When touching a number pad, two figures or more are displayed.
c) When touching the pads, sometimes a pad produces no signal.
2. Control Panel
The following symptoms indicate a defective control unit. Before replacing the control unit perform the
key unit test (Procedure P) to determine if control unit is faulty.
2-1  In connection with pads
a) When touching the pads, a certain group of pads do not produce a signal.
b) When touching the pads, no pads produce a signal.
2-2  In connection with indicators
a) At a certain digit, all or some segments do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light up.
d) The corresponding segments of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f) A certain group of indicators do not light up.
g) The figure of all digits flicker.
2-3  Other possible troubles caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
d) Proper temperature measurement is not obtained.
G 8
G 7
G 6
G 5
G 4
G 3
G 2
G 1
G12
G11
G10
G 9
ROAST BEEF / LAMB
WHOLE POULTRY
CHICKEN QUARTERS
CHICKEN QUARTERS (INSTANT COOK)
ROAST PORK
PASTA DISH
RISOTTO
GRATIN
MEAT JOINT
OVEN CHIPS
ROAST POULTRY
GRILL
MICRO.
POWER
DUAL CONV. /
GRILL
CONV.
( ˚C ) 
DOWN
LESS
MORE
UP
CLEAR
AUTO MINUTE
STOP
START
KITCHEN TIMER
CLOCK SET
KG / LB
CONVERSION
BREAKFAST
BAKED POTATOES
PIZZA
If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon
cable is making good contact, verify that the stop switch operates properly; that is the contacts
are closed when the door is closed and open when the door is open. If the stop switch is good,
disconnect the flat ribbon cable that connects the key unit to the control unit and make sure the
stop switch is closed (either close the door or short the stop switch connecter). Use the Key unit
matrix indicated on the control panel schematic and place a jumper wire between the pins that
correspond to the STOP/CLEAR pad making momentary contact. If the control unit responds by
clearing with a beep the key unit is faulty and must be replaced. If the control unit does not
respond, it is faulty and must be replaced.  If a specific pad does not respond, the above method
may be used (after clearing the control unit) to determine if the control unit or key pad is at fault.
CARRY OUT 4R CHECKS.
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